Numerous biotechnological processes require temperature cycling within a defined range. These include peptide sequencing, DNA construction, DNA amplification, denaturation kinetics and probe research.
Various instruments have been constructed to provide temperature cycling. These are typically water or oil baths such as the one provided by Perkin-Elmer which includes a recirculating oil bath with chillers and heaters in an aluminum block. It is programmable and will run a preselected temperature profile. It controls the temperature of up to 48 test tubes and utilizes one or two temperature sensors to sense the proper temperatures.
In this and other prior devices, precise temperature regulation has been found difficult to attain. Systems which rely upon circulating liquids for temperature control tend to have many moving parts which can fail, and the recirculating liquids cannot accurately control temperature. Temperature ramping in such liquid systems tends to be non-uniform over time because of a gradual drift of the controlling liquids towards equilibrium. In the Perkin-Elmer apparatus, oil may contaminate the outside of the sample tubes. Further disadvantages may include the necessity to adjust the cycling to accommodate changing environmental conditions, and multiple diagnostic tests to assess the instrument's performance. Water bath systems also have a slow response time, and require expensive, large capacity water baths.